Temporomandibular muscle and joint disorders (TMJD) are common conditions with a substantial public health burden. Although TMJD patients commonly have temporomandibular joint (TMJ) intra- articular disorders, including disc displacement (DD) and osteoarthritis (OA), the clinical significance of these disorders and their causal relationship to persistent jaw pain and dysfunction are poorly understood. The recently completed Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Validation Project (U01 DEO13331) demonstrated that 1) TMJ imaging is required to diagnose TMJ intra-articular disorders; and 2) cross-sectional data show that radiographically diagnosed DD and OA are significantly associated with jaw pain, jaw functional limitations and disability. It is therefore critical that we assess longitudinally whether these cross-sectional findings can be supported. Given that the available Validation Project cohort was assembled at a cost of $8.2 million, it is unlikely that there will be another similar cohort in the future to investigate the question, one of great significance to the public health: Are TMJ intra-articular disorders causally related to patient-reported outcomes of jaw pain intensity, jaw function and disability? Study participants will be recalled from the Validation Project cohort 9 years after their initial comprehensive examination was completed. Their physical status will be re-assessed, and progression of their intra-articular joint diagnoses will be measured by comparing bilateral TMJ MRI and CT at follow-up to baseline imaging. The subjects' psychosocial status will also be re-assessed along with the primary outcome measures of pain intensity, jaw functional limitations, and disability that are core domains recommended for assessment by Initiative on Methods, Measurement and Pain Assessment in Clinical Trials (IMMPACT). The study will assess when, and under what circumstances, intra-articular disorders progress and whether this progression is associated with increased jaw pain, jaw limitations and disability. We will also determine, as a secondary aim, which baseline biological and psychosocial factors are predictors for progression of TMJ DD and OA at follow-up. The ultimate goal is to determine the degree to which progressive change in intra-articular disorders contributes to pain and dysfunction outcomes, within the context of the biopsychosocial model. This project will provide knowledge necessary for development of evidence-based guidelines for TMJD diagnosis and management, as well as contribute to cost effective imaging and elimination of unnecessary diagnostic radiation.